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  • Chemistry  (19)
  • Key words Helianthus annuus  (2)
  • Animals
  • Life and Medical Sciences
  • Quantum optics, physics of lasers, nonlinear optics, classical optics
  • 1995-1999  (23)
  • 1999  (9)
  • 1998  (14)
Collection
Keywords
Publisher
Years
  • 1995-1999  (23)
Year
  • 1
    Electronic Resource
    Electronic Resource
    New Imidazabole Derivatives: Dimers of Carbene-Borane Adducts (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1547-1553 
    Details
    ISSN: 1434-1948
    Keywords: Imidazaboles ; Carbene-borane adducts ; Azole-borane adducts ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation and characterization of five new imidazabole derivatives is reported: 1,5-dibenzyl-4,4,8,8-tetrahydroimidazabole (2), 4,4,8,8-tetrafluoro-1,5-dimethylimidazabole (3), 4,4-difluoro-8,8-dihydro-1,5-dimethylimidazabole (4), 4,4,8,8-tetrachloro-1,5-dimethylimidazabole (5), and 4,4,8,8-tetraethyl-1,5-dimethylimidazabole (6). The structures of compounds 2-6 as dimeric carbene-borane adducts rather than dimeric N-borane adducts are discussed on the basis of NMR (2-6) and X-ray diffraction data (2, 3, 5 and 6).
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  • 2
    Electronic Resource
    Electronic Resource
    Syntheses and Characterization by NMR Spectroscopy and X-ray Diffraction of Complexes Derived from Metals of Groups 2 and 13 and the Ligand Bis(3,5-di-tert-butyl-1-hydroxy-2-phenyl)amine (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1021-1027 
    Details
    ISSN: 1434-1948
    Keywords: Alkaline earth metals ; Group-13 metals ; Coordination chemistry ; Bis(3,5-di-tert-butyl-1-hydroxy-2-phenyl)amine ligand ; Nonacoordinated strontium compound ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of 3,5-di-tert-butylcatechol and aqueous ammonia with boron, aluminum, gallium, or strontium chloride, or with calcium or barium acetate produce, under oxidizing conditions, neutral complexes of stoichiometric formulae ML (M = BCl), ML2, [M = Al (2), Ga (3), Ca (4), and Ba (5)], and ML3H [M = Sr (6)] [L = different oxidation states of bis(3,5-di-tert-butyl-1-hydroxy-2-phenyl)amine]. The structures of 1 and 4-6 were established by 1H- and 13C-NMR spectroscopy and of 2, 3, and 6 by X-ray diffraction. The coordination compound ClBL (1) was obtained by transmetallation of ZnL2 with BCl3. It is a tetracyclic compound with tetracoordinated boron and nitrogen atoms, the ligand being in the reduced form, bis(hydroxyphenyl)amine. The paramagnetic complexes 2 and 3 crystallized in the triclinic system and are hexacoordinated with two orthogonal planar ligands bonded to the metal atoms. The ligands appear in two different oxidation states: one as the monoanion and another as a radical dianion. Based on their X-ray diffraction molecular structures, it is deduced that both ligands have similar structures, confirming electronic delocalization and fast interconversion of their oxidation states. Ca and Ba complexes are diamagnetic and hexacoordinated, both ligands being monoanions The strontium complex crystallized in the monoclinic system, the metal atom is nonacoordinated, having two ligands as monoanions, and a third one is a neutral protonated diquinone. Its structure is a distorted helix with three paddles in a C3 geometry and its unexpected diamagnetic behaviour is due to the presence of a reduced protonated ligand.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Inheritance of high palmitic acid content in the seed oil of sunflower mutant CAS-5 (1999)
    Springer
    Theoretical and applied genetics 98 (1999), S. 496-501 
    Details
    ISSN: 1432-2242
    Keywords: Key words Helianthus annuus ; Sunflower mutant ; Palmitic acid ; Inheritance ; Fatty acid composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Sunflower genotypes with increased levels of palmitic acid (C16 : 0) in the seed oil could be useful for food and industrial applications. The objective of the present study was to determine the inheritance of the high C16 : 0 content in the sunflower mutant line CAS-5 (〉25% of the total oil fatty acids). This mutant was reciprocally crossed with the lines HA-89 (5.7% C16 : 0) and BSD-2-691 (5.4% C16 : 0), the latter being the parental line from which CAS-5 was isolated. No maternal effect for the C16 : 0 content was observed from the analysis of F1 seeds in any of the crosses. The inheritance study of the C16 : 0 content in F1, F2 and BC1F1 seeds from the crosses of CAS-5 with its parental line BSD-2-691 indicated that the segregation fitted a model of two alleles at one locus with partial dominance for the low content. The analysis of the fatty acid composition in the F2 populations from the crosses with HA-89 revealed a segregation fitting a ratio 19 : 38 : 7 for low (〈7.5%), middle (7.5–15%), and high (〉25%) C16 : 0 content, respectively. This segregation was explained on the basis of three loci (P1, P2, P3) each having two alleles showing partial dominance for low content. The genotypes with a high C16 : 0 content were homozygous for the recessive allele p1 and for at least one of the other two recessive alleles, p2 or p3. This model was further confirmed with the analysis of the F3 and the BC1F1 generations. It was concluded that both the recessive alleles p2 and p3 were already present in the BSD-2-691 line, the allele p1 being the result of a mutation from P1. This genetic study will facilitate breeding strategies associated with the incorporation of the high C16 : 0 trait into agronomically acceptable sunflower hybrids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220051097
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  • 4
    Electronic Resource
    Electronic Resource
    Genetic control of high stearic acid content in the seed oil of the sunflower mutant CAS-3 (1999)
    Springer
    Theoretical and applied genetics 99 (1999), S. 663-669 
    Details
    ISSN: 1432-2242
    Keywords: Key words Helianthus annuus ; Sunflower mutant ; Stearic acid ; Oil quality ; Genetic control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A sunflower mutant, CAS-3, with about 25% stearic acid (C18:0) in the seed oil was recently isolated after a chemical-mutagen treatment of RDF-1-532 seeds (8% C18:0). To study the inheritance of the high C18:0 content, CAS-3 was reciprocally crossed to RDF-1–532 and HA-89 (5% C18:0). Significant reciprocal-cross differences were found in one of the two crosses, indicating possible maternal effects. In the CAS-3 and RDF-1–532 crosses, the segregation patterns of the F1, BC1, and F2 populations fitted a one-locus (designated Es1) model with two alleles (Es1, es1) and with partial dominance of low over high C18:0 content. Segregation patterns in the CAS-3 and HA-89 crosses indicated the presence of a second independent locus (designated Es2) with two alleles (Es2, es2), also with partial dominance of low over high C18:0 content. From these results, the proposed genotypes (C18:0 content) of each parent were as follows: CAS-3 (25.0% C18:0) =es1es1es2es2; RDF-1–532 (8.0% C18:0) =Es1Es1es2es2; and HA-89 (4.6% C18:0) =Es1Es1Es2Es2. The relationship between the proposed genotypes and their C18:0 content indicates that the Es1 locus has a greater effect on the C18:0 content than the Es2 locus. Apparently, the mutagenic treatment caused a mutation of Es1 to es1 in RDF-1–532.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220051282
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis and properties of stereoregular poly(ester amides) derived from carbohydrates (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 67-77 
    Details
    ISSN: 0887-624X
    Keywords: stereoregular poly(ester amides) ; carbohydrate-based polymers ; polycondensation reactions ; chiral polymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two poly(ester amides) containing three methoxy groups stereoregularly attached to the main chain have been prepared by using naturally occurring L-arabinose and D-xylose as the starting materials. The polymers were prepared by the active ester polycondensation method and characterized by elemental analysis, IR, and 1H- and 13C-NMR spectroscopies. Both viscosimetry and GPC were used to estimate the molecular weights. The polymers are hydrophilic, one of them being water soluble, and exhibited moderate optical activity. Thermal and X-ray diffraction studies revealed that they are slightly crystalline and stable up to 250°C under nitrogen. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 67-77, 1998
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  • 6
    Electronic Resource
    Electronic Resource
    A theoretical study of the comonomer effect in the ethylene polymerization with zirconocene catalytic systems (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1157-1167 
    Details
    ISSN: 0887-624X
    Keywords: zirconocene catalysts ; ethylene ; 1-hexene ; copolymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The PM3(tm) semiempirical method has been used to optimize the structures for the reactants and transition states of the first and second ethylene insertion processes into zirconocene catalytic systems. The results obtained for these reactions are compared with calculations published in the literature performed at different ab-initio theoretical levels. The agreement between our calculations and those reported in the literature is satisfactory. Taking advantage of the reduced computational effort required in semiempirical calculations two additional processes related with the so-called comonomer effect were also studied: ethylene/1-hexene copolymerization, and chain termination reaction, both in the homopolymerization and in copolymerization of ethylene with 1-hexene comonomer. The calculated activation energies support some experimental findings such as the higher polymerization activities in the presence of comonomers and also the molecular weight reduction of the copolymers due to the more favorable β-elimination reactions. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1157-1167, 1998
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis of Analogues of Brassinosteroids from Chenodeoxycholic Acid (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2405-2407 
    Details
    ISSN: 1434-193X
    Keywords: Natural products ; Steroids ; Chenodeoxycholic acid ; Brassinosteroid analogues ; Biological activity ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and spectroscopic characterization of two new bioactive analogues of brassinosteroids with a 24-hydroxylated cholanic side chain, an A/B ring cis-junction and oxygenated functions in C-7 is described.
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  • 8
    Electronic Resource
    Electronic Resource
    HRGC/FID and HRGC/MSD Analysis of the Secondary Metabolites Obtained by Different Extraction Methods from Lepechinia schiedeana, and in Vitro Evaluation of Its Antioxidant Activity (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 343-349 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; gas chromatography-mass spectrometry ; essential oil analysis ; Lepechinia schiedeana ; antioxidant activity ; lipid peroxidation ; Ledol; Ledol HMQC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Steam distillation (SD), simultaneous distillation-solvent extraction (SDE), microwave-assisted solvent extraction (MWE), and supercritical (CO2) extraction (SFE) were used to isolate secondary metabolites from Lepechinia schiedeana. The various extracts were analyzed by capillary gas-chromatography, on poly (dimethylsiloxane) (DB-1) and poly(ethyleneglycol) (INNOWAX), 60 m columns, using FID or MSD (EI, 70 eV). Kováts indexes, mass spectra, or standard compounds were employed for compound identification. 43, 61, 67, and 79 compounds at concentrations above 0.01% were detected in the SD, SDE, MWE, and SFE extracts, respectively. Ledol, C15H26O, was the major constituent (20.04-36.87%) in all extracts. Oxygenated sesquiterpenes (24.36-43.14%), C10H16, monoterpenes (27.70-39.87%), and C15H24, sesquiterpenes (10.04-22.22%) were the main groups of compounds present in SD, SDE, MWE, and SFE extracts. Heavy hydrocarbons (Cn 〉 15), diterpenoids, and phytosterols were found only in MWE and SFE extracts. The antioxidant activity of Lepechinia schiedeana was measured by the HRGC quantification of the volatile carbonyl compounds, final products of lipoxidation, released in a model lipid system (sunflower oil) by the effect of the Fenton reagent. The concentration of volatile carbonyl compounds decreased by 65% when lipid oxidation was induced in the presence of macerated Lepechinia plant. The protection of polyunsaturated acids in sunflower oil was also studied by measuring their concentrations after heating of the oil (180°C, 2 h) with and without macerated Lepechinia plant.
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  • 9
    Electronic Resource
    Electronic Resource
    A Trinuclear Palladium(II) Complex with Bridging 2-Hydroxyacetophenone N4-Ethylthiosemicarbazone Ligands - An Unusual Dimethylformamide Promoted Deprotonation and Aggregation (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 861-863 
    Details
    ISSN: 1434-1948
    Keywords: Trinuclear triangulo palladium complex ; 2-Hydroxyacetophenone N4-ethylthiosemicarbazone ; Dimethylformamide aggregation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The X-ray crystal structure of a palladium(II) complex of 2-hydroxyacetophenone N4-ethylthiosemicarbazone (H2Ap4E) shows it to be a triangular,trinuclear complex with bridging thiosemicarbazonato sulfur atoms. This species can be formed from a monomer on dissolution in DMF or directly from Li2PdCl4 and the thiosemicarbazone in methanol-ammonia solution.
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  • 10
    Electronic Resource
    Electronic Resource
    The 3,5-Dichlorotrifluorophenyl Ligand, a Useful Tool for the Study of Coordination Modes and Dynamic Behavior of Complexes of Palladium and Platinum (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1745-1753 
    Details
    ISSN: 1434-1948
    Keywords: Palladium ; Platinum ; Aryl rotation ; Through-space coupling interactions ; Turnstile mechanism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The square-planar complexes [MR2L2] (M = Pd, Pt; R = 3,5-C6Cl2F3) [L2 = OPPyPh2 (Py = 2-pyridyl); SPPyPh2; OPPy2Ph; DMBI (3,3′-dimethyl-2,2′-biindazole); OPPyPh(NHTol-p); p-TolNPPy2Ph] have been prepared by treating cis-[MR2(THF)2] (THF = tetrahydrofuran) with the appropriate chelate ligands. The 19F-NMR spectra of these complexes show the presence of intramolecular through-space F-F couplings between ortho-fluorine atoms of nonequivalent R groups, which provide information for the assignment of the different ortho-fluorine signals and can be used to study the dynamic behavior of the mentioned complexes such as: a) Rotation of the R group in either Pd or Pt complexes, at the same or at different rates for each R groups depending on the neutral ligand; and b) exchange of the coordination sites of the chelating ligand, either by Berry or by turnstile mechanisms. The activation parameters for some of the processes are given.
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